This invention relates generally to the cleaning of semiconductor materials and specifically to the post silica polish cleaning of semiconductor wafers.
With the advent of microminiaturization of electronic devices, the need for damage-free, smooth and clean semiconductor wafer surfaces has become increasingly important. Smooth, polished surfaces are obtained by the use of polishing slurries. Silica polishing is an example of a typical polishing process. In the silica polishing process, a polishing slurry is used which includes a colloidal silicon dioxide abrasive, sodium dichloroisocyanurate as an oxidizing agent, and sodium carbonate as a base. The pH of the polishing slurry is below 10. After polishing, it is necessary to clean the polished surface to remove the polishing slurry and other surface contaminants with a minimum of chemical or mechanical surface damage.
At the end of the silica polishing process, removal of the following materials from the wafer surface must be considered in order to produce a clean surface:
1. Colloidal silicon dioxide. PA1 2. Sodium dichloro-isocyanurate and its reaction products with sodium carbonate. PA1 3. Sodium carbonate. PA1 4. Amorphous silicon dioxide. PA1 5. Other metallic impurities deposited on silicon surfaces from slurry components. PA1 R.sub.2 and R.sub.3 and R.sub.4 are lower alkyl and substituted lower alkyl groups and various combinations thereof such as methyl, ethyl, propyl, benzyl, etc., and PA1 X.sup.- is an anion.
Various mechanical and chemical processes have been used to clean silica or other metal oxide based slurry polished wafers. These processes either produce mechanical damage, change the surface characteristics significantly, or use chemicals which present environmental and/or hygienic considerations. Most of the chemical methods produce hydrophillic surfaces which are susceptible to reaction with atmospheric contaminants.
A new physico-chemical process has been found which results in a clean, hydrophobic semiconductor surface without damaging the surface.